WATER JET CONFERENCE - Waterjet Technology Association

shell is "shot," the energy is transmitted by the water to the concrete, causing it to crack.
There is the possibility that several holes can be drilled in a line and "shot"
simultaneously which would define a reasonably straight fracture plane. The design of
this particular device is not suited for thin (12-in.-thick) concrete slabs. With some
modification(s) it could prove to be a forerunner in the search for acceptable concrete
cutting techniques. The speed of cut is mainly determined by the rate the holes can be
drilled, assuming several holes/devices will be used in tandem (Styron, 1982b).
Another combination of methods employs a concrete saw to cut the slab 6 in.
deep instead of 12 in. A mechanical impactor (jack hammer) device is used to break the
concrete away from the remaining segment. The broken part of the remaining concrete
may he used to provide a supporting surface for the replacement surface.
DATA TABULATION
The data search for specifics concerning various methods of cutting concrete was
frustrating. At the start, a data sheet was prepared listing cutting method, cutting rate, fuel
type employed, fuel consumption at the stated rate, water consumption (spillage/overflow
that would probably find its way into the crater) , noise level, number of personnel
required, and pertinent comments. The intent was to determine the time required to cut
400 sq ft and the gallons of fuel needed. Not one single report, brochure, or document
listed all the desired information. Additionally, very few limitations were noted, although
most mentioned that antifreeze would be necessary for water-lubricated/cooled cutting
devices operating in freezing weather. Some indicated the most important variable in
cutting un-reinforced concrete is the type of aggregate - those formed from silica and
quartzite being extremely hard and difficult to cut. The lack of information is
understandable when one considers that concrete hardness (compressive strength and
type of aggregate employed) (Mellor, 1975) and concrete depth vary as does the depth of
cut employed. These three variables have a significant impact on the rate of cut (exposure
rate) realized.
The data presented below are separated by the type of technology used to cut/
break the concrete. The exposure rate and the technology level, if commercially available
or a research and development item, are tabulated (Tables 1 - 4), together with major
technical issues and/or remarks noted.
Concrete Saw. Concrete cutting saws are mechanical devices that currently enjoy 80% of
the concrete cutting market ( Kubo et al., 1981). Two basic types are in use -- the
carbide-tipped saw and the diamond-blade saw. The carbide-tipped saw technology is
based on the abrasive removal of concrete using a hard carbide-tipped saw with sufficient
power. Blade speed is important since blade wear and maintenance increase with blade
speed. Blade life is the main issue. Equipment mobility under the expected use conditions
are suspect. Blade lubricant/coolant is required by some but not by others. The
diamond-blade saw is generally the faster of the two (Table 1) and reportedly quieter (no
details/ data stated). Most saws in operation today use diamond blades. Care must he
taken and a certain amount of expertise is desirable because at high blade speeds the
impact between the diamond particles used to cut the concrete and the concrete can break
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